1. Field of the Invention
The present invention relates to the field of power supplies. More specifically, the present invention relates to a method and an apparatus for increasing reliability of redundant power supplies.
2. Description of the Related Art
Computer systems are information handling systems that may be designed to give independent computing power to one or a plurality of users. An information handling system, as referred to herein, is defined as an xe2x80x9cinstrumentality or aggregate of instrumentalities primarily designed to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle or utilize any form of information, intelligence or data for business, scientific, control or other purposes.xe2x80x9d Computer systems may be found in many forms including, for example, mainframes, minicomputers, workstations, servers, clients, personal computers, Internet terminals, notebooks, personal digital assistants, and embedded systems. Personal computer (xe2x80x9cPCxe2x80x9d) systems, such as the International Business Machines (IBM) compatible PC systems, include desktop, floor standing, or portable versions. A typical computer system is a microcomputer that includes a system processor or microprocessor, associated memory and control logic, and a number of peripheral devices that provide input and output for the system. Such peripheral devices often include display monitors, keyboards, mouse-type input devices, floppy and hard disk drives, optical drives, and printers. The number of devices being added to computer systems continues to grow. For example, many computer systems also include network capability, terminal devices, modems, sound devices, voice recognition devices, electronic pen devices, and mass storage devices such as tape drives, CD-ROM drives, or DVDs.
Typically, computer systems are powered by a power supply system that receives and converts alternating current (AC) power to direct current (DC) power that is used to power the computer system components such as the system processor. A power supply system typically includes electrical components for the conversion of available power of one set of characteristics to another set of characteristics to meet specified requirements. Typical application of power supplies include converting raw input power to a controlled or stabilized voltage and/or current for the operation of electronic equipment. A regulated power supply system typically provides a built-in controller to regulate the power output in response to a set point input.
In one type of AC-DC power supply used to supply current at DC voltages, power is converted from an AC power source, such as 120 V, 60 Hz or 220 V, 50 Hz power, from a wall outlet. This is accomplished by first rectifying the AC voltage of the power source to an unregulated DC voltage. The unregulated DC voltage typically has a ripple waveform component. To xe2x80x9csmoothxe2x80x9d the ripple component, most power supplies incorporate a bulk filter capacitor or bulk reservoir capacitor. Typically, a bulk filter capacitor stores charge during the ripple peaks and releases charge during the low portion of the ripple cycle. In addition, AC-DC power supplies may typically include a DC-DC converter for providing DC power to the computer system within specified tolerances.
To improve the availability and reliability of power supply systems it is well known to configure redundant power supply systems. Typically, in a redundant configuration one or more power supply systems may be coupled to share a load current such that failure of a single power supply system may not substantially affect the load current. FIG. 1 (PRIOR ART) illustrates a typical redundant power supply system configured in a current load sharing arrangement. The redundant power supply system includes power supplies PS1115 and PS2116 configured to share the power provided to a load, e.g., an electronics system 110. Typically each of the power supplies is regulated and is configured to share the total current load equally. A current balance circuit 120 accomplishes the task of balancing the current load equally between PS1115 and PS2116. A feedback output signal 125 is generated by the current balance circuit 120 in response to receiving the current sense #1 130 and current sense #2 135 inputs. The feedback output signal 125 is provided to control the current output of Power Supply #1 115 such that current sense #1 130 and current sense #2 135 are maintained to be substantially equal.
Traditional configuration of a redundant power supply system, e.g., as illustrated in FIG. 1 (PRIOR ART), typically has not provided sufficient consideration for operational stress factors, e.g., temperature. It is well known that power supply systems operating under a greater operational stress are more likely to fail. In a redundant power supply system configuration what is needed is a load sharing strategy, which considers the operational stress factors in determining the load allocation among the redundant power supply systems to increase the overall reliability and availability.
In accordance with the present invention, a method of sharing a load current among a plurality of power supply systems and an apparatus thereof is described.
In one embodiment, a method of sharing a load current among a plurality of power supply systems includes measuring an output current and at least one variable representing an operational stress factor associated with the power supply system for each of the plurality of power supply systems. The current output of at least one of the plurality of power supplies is adjusted as a function of the at least one measured variable that represents the operational stress factor.
In one embodiment, the apparatus for sharing a load current among a redundant power supply system includes a first power supply system coupled to a second power supply system. The apparatus also includes a balance circuit configured to receive two inputs. A first input represents a current output of the second power supply system and a second input represents the at least one measured variable associated with the first power supply system. The balance circuit is operable to provide a feedback output to the first power supply system in response to the received inputs.
In one embodiment, a computer system includes a processor, a memory coupled to the processor and a plurality of power supply systems configured to implement the method of sharing a load current, the load being the power provided to the processor and the memory. The plurality of power supply systems include a first sensor to measure a current output of each of the plurality of power supply systems and a second sensor to measure at least one variable representing an operational stress factor associated with each of the plurality of power supply systems. The plurality of power supply systems also include a controller configured to receive inputs from the first and second sensor. The controller is operable to adjust the current output of at least one of the plurality of power supply systems in response to the received inputs.
In one embodiment, a computer system includes a processor, a memory coupled to the processor and a redundant power supply system configured to implement the method of sharing a load current, the load being the power provided to the processor and the memory. The redundant power supply system includes a first power supply system coupled to a second power supply system. The redundant power supply system also includes a controller configured to receive two inputs and provide a feedback output. The controller is configured to receive a first input representing a current output of the second power supply system and a second input representing at least one variable of an operational stress factor associated with the first power supply system. In response to receiving the two inputs the controller provides a feedback output to the first power supply system. The output current of the first power supply system may be adjusted in response to the feedback output signal received from the controller.